pgsql: Put tests of md5() function into separate test file

Put tests of md5() function into separate test file

In FIPS mode, these calls will fail. By having them in a separate
file, it would make it easier to have an alternative output file or
selectively disable these tests. This isn't done here; this is just
some preparation.

Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
Discussion: https://www.postgresql.org/message-id/647f6cc1-473d-f788-ade0-c09201e5ab6a@enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/9786b89bd1b4c298ed900d118cbb5eb997c34905

Modified Files
--------------
src/test/regress/expected/md5.out | 91 +++++++++++++++++++++++++++++++++++
src/test/regress/expected/strings.out | 88 ---------------------------------
src/test/regress/parallel_schedule | 2 +-
src/test/regress/sql/md5.sql | 36 ++++++++++++++
src/test/regress/sql/strings.sql | 32 ------------
5 files changed, 128 insertions(+), 121 deletions(-)